1. Field of the Invention
The present invention relates to a piezoelectric transformer component suitable for use in a device including multiple voltage circuits and required to be small in size and be highly reliable, such as a portable multimedia device. More particularly, this invention relates to a highly-reliable small-sized piezoelectric transformer component including a silicon substrate and a piezoelectric vibrator made of a piezoelectric thin film formed on the silicon substrate, which are integrally formed in a monolithic structure so as to be easily sealed.
2. Description of the Related Art
There is always a market demand for downsizing electronic devices, and there is also a demand for reducing size and weight of components for use in these devices. This tendency is especially pronounced for portable multimedia devices, which have recently been rapidly widespread, and there is a great demand for reducing size and weight of components for use in these devices.
It is also demanded that such components for use in the portable devices have a high reliability so that the portable devices can operate with stability against shock or the like that occurs during their use.
Meanwhile, an electromagnetic transformer takes the role of performing voltage conversion in an electric circuit. However, the electromagnetic transformer has a structure in which an electric wire is wound in coil form around a core member such as a ferrite core, accordingly is likely to become large in size, and thus has a difficulty in meeting the demand for size reduction.
Thus, a piezoelectric transformer has come into practical use in place of the electromagnetic transformer. The piezoelectric transformer performs voltage conversion, using piezoelectric phenomenon, by temporarily converting an alternating current signal applied to a piezoelectric body into mechanical vibration and then by reconverting the vibration into an electric signal. Since the piezoelectric transformer need not include a winding and thus is simple in structure, it has the advantage of being downsizable. In particular, the piezoelectric transformer has the advantage of being able to achieve height reduction and thus is suitable for a step-up transformer for use in a liquid crystal backlight. Accordingly, the piezoelectric transformer is being used in various applications.
In a typical piezoelectric transformer, a vibrator needs to be supported and sealed therein since the piezoelectric transformer operates by vibrating the piezoelectric body. As can be seen from a configuration disclosed in Japanese Patent Application Publication No. 2003-309300, a ceramic vibrator serving as the vibrator is supported by pressure with a certain component, and is sealed in a resin case. Also, a technique disclosed in Japanese Patent Application Publication No. 2007-19097 achieves the size and thickness reduction of the piezoelectric transformer; however, an element structure of a piezoelectric vibrator is complicated, and thus, the technique presents a problem in terms of reliability.